Loss of wobble uridine modification in tRNA anticodons interferes with TOR pathway signaling
Authors:Viktor Scheidt1,#, André Jüdes1,#, Christian Bär1,2,#, Roland Klassen1 and Raffael Schaffrath1
1 Institut für Biologie, Abteilung Mikrobiologie, Universität Kassel, D-34132 Kassel, Germany.
2 Present address: Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Melchor Fernandez Almagro 3, Madrid, Spain.
# These authors contributed equally to the study.
Keywords:
Saccharomyces cerevisiae, TOR signaling, rapamycin, Gln3, NCR, Sit4, Elongator complex, tRNA anticodon modification, tRNase zymocin.
Abbreviations:
NCR - nitrogen catabolite repression,
PP2A - type 2A protein phosphatases,
PPIases - peptidyl-prolyl cis/trans-isomerases,
TOR - target of rapamycin.
Related Article(s)?
Patrick C. Thiaville and Valérie de CrécyLagard (2015). The emerging role of complex modifications of tRNALysUUU in signaling pathways. Microbial Cell 2(1): 1-4., 10.15698/mic2015.01.185
Corresponding Author(s):
Conflict of interest statement:
The authors declare there is no conflict of interest.
Please cite this article as:
Viktor Scheidt, André Jüdes, Christian Bär, Roland Klassen and Raffael Schaffrath (2014). Loss of wobble uridine modification in tRNA anticodons interferes with TOR pathway signaling. Microbial Cell 1(12): 416-424.
© 2014 Scheidt et al. This is an open-access article released under the terms of the Creative Commons Attribution (CC BY) license, which allows the unrestricted use, distribution, and reproduction in any medium, provided the original author and source are acknowledged.
Abstract:
Previous work in yeast has suggested that modification of tRNAs, in particular uridine bases in the anticodon wobble position (U34), is linked to TOR (target of rapamycin) signaling. Hence, U34 modification mutants were found to be hypersensitive to TOR inhibition by rapamycin. To study whether this involves inappropriate TOR signaling, we examined interaction between mutations in TOR pathway genes (tip41∆, sap190∆, ppm1∆, rrd1∆) and U34 modification defects (elp3∆, kti12∆, urm1∆, ncs2∆) and found the rapamycin hypersensitivity in the latter is epistatic to drug resistance of the former. Epistasis, however, is abolished in tandem with a gln3∆ deletion, which inactivates transcription factor Gln3 required for TOR-sensitive activation of NCR (nitrogen catabolite repression) genes. In line with nuclear import of Gln3 being under control of TOR and dephosphorylation by the Sit4 phosphatase, we identify novel TOR-sensitive sit4 mutations that confer rapamycin resistance and importantly, mislocalise Gln3 when TOR is inhibited. This is similar to gln3∆ cells, which abolish the rapamycin hypersensitivity of U34 modification mutants, and suggests TOR deregulation due to tRNA undermodification operates through Gln3. In line with this, loss of U34 modifications (elp3∆, urm1∆) enhances nuclear import of and NCR gene activation (MEP2, GAP1) by Gln3 when TOR activity is low. Strikingly, this stimulatory effect onto Gln3 is suppressed by overexpression of tRNAs that usually carry the U34 modifications. Collectively, our data suggest that proper TOR signaling requires intact tRNA modifications and that loss of U34 modifications impinges on the TOR-sensitive NCR branch via Gln3 misregulation.
doi: 10.15698/mic2014.12.179
Volume 1, pp. 416 to 424, published 29/11/2014.